The present application relates to the field of radiology imaging. It finds particular application to radiology imaging modalities that can employ photon counting techniques. For example, medical, security, and/or industrial applications may utilize a computed tomography (CT) scanner or a projection radiography imaging modality (e.g., a digital radiography imaging modality) to count a number of X-ray and/or gamma photons that traverse an object under examination and that are detected by a photon counting detector array. Based upon the number of photons detected, one or more images providing a two-dimensional representation, three-dimensional representation, four-dimensional representation (e.g., dynamic three-dimensional representation) and/or five-dimensional representation (e.g., dynamic multi-spectral three-dimensional representation) of an object under examination may be generated therefrom.
Today, CT and other radiology imaging modalities (e.g., single-photon emission computed tomography (SPECT), mammography, projection radiography, etc.) are useful to provide information, or images, of interior aspects of an object under examination. Generally, the object is exposed to radiation comprising photons (e.g., such as X-rays, gamma rays, etc.), and an image(s) is formed based upon the radiation absorbed and/or attenuated by the interior aspects of the object, or rather an amount of photons that is able to pass through the object. Generally, highly dense aspects of the object absorb and/or attenuate more radiation than less dense aspects, and thus an aspect having a higher density, such as a bone or metal, for example, will be apparent when surrounded by less dense aspects, such as muscle or clothing.
Radiology imaging modalities generally comprise, among other things, a detector array comprised of a plurality of detector cells that are respectively configured to convert radiation that has traversed the object into electrical signals that may be processed to produce the image(s). The cells are typically “chargeinteg-rating” and/or “photon counting ” type cells (e.g., the imaging modality operates in charge integration mode, photon counting mode, or both).
Photon counting cells are configured to convert energy into electrical signals that are proportional to the energy of a detected photon (e.g., at times referred to as a detection event). Thus, ideally, signals produced by respective cells generally comprise one or more current and/or voltage pulses, for example, respectively associated with a single detection event. A controller may then be used to determine the location and energy of respective detection events, accumulate the detection events occurring during a measurement interval (e.g., an “acquisition view”), digitize the information, and/or process the digital information to form an image, for example. It may be appreciated that there are numerous advantages to photon counting cells over charge integrating cells. For example, the counting of photons is substantially devoid of electronic noise (e.g., apart from the inherent random nature of photon emissions, which may be modeled by a Poisson random variable). Therefore, a lower dose of radiation may be applied to the object under examination. Moreover, photon counting cells generally allow for energy or wavelength discrimination. Therefore, images resulting from radiation emitted at different energy levels may be obtained at the same or substantially the same time, for example.